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Process for making piperidinone carboxamide indane and azainane derivatives, which are CGRP receptor antagonists useful for the treatment of migraine. This class of compounds is described in U.S. Patent Application Nos. 13/293,166 filed November 10, 2011 , 13/293, 177 filed November 10, 2011 and 13/293,186 filed November 10, 2011, and PCT International Application Nos. PCT/US11/60081 filed November 10, 2011 and PCT/US 11/60083 filed November 10, 2011.

CGRP (Calcitonin Gene-Related Peptide) is a naturally occurring 37-amino acid peptide that is generated by tissue-specific alternate processing of calcitonin messehger RNA and is widely distributed in the central and peripheral nervous system. CGRP is localized predominantly in sensory afferent and central neurons and mediates several biological actions, including vasodilation. CGRP is expressed in alpha- and beta-forms that vary by one and three amino acids in the rat and human, respectively. CGRP-alpha and CGRP-beta display similar biological properties. When released from the cell, CGRP initiates its biological responses by binding to specific cell surface receptors that are predominantly coupled to the activation of adenylyl cyclase. CGRP receptors have been identified and pharmacologically evaluated in several tissues and cells, including those of brain, cardiovascular, endothelial, and smooth muscle origin.

Based on pharmacological properties, these receptors are divided into at least two subtypes, denoted CGRPi and CGRP2. Human oc-CGRP-(8-37), a fragment of CGRP that lacks seven N-terminal amino acid residues, is a selective antagonist of CGRP l, whereas the linear analogue of CGRP, diacetoamido methyl cysteine CGRP ([Cys(ACM)2,7]CGRP), is a selective agonist of CGRP2. CGRP is a potent neuromodulator that has been implicated in the pathology of cerebrovascular disorders such as migraine and cluster headache. In clinical studies, elevated levels of CGRP in the jugular vein were found to occur during migraine attacks (Goadsby et al., Ann. Neurol., 1990, 28, 183-187), salivary levels of CGRP are elevated in migraine subjects between attacks (Bellamy et al., Headache, 2006, 46, 24-33), and CGRP itself has been shown to trigger migrainous headache (Lassen et al., Cephalalgia, 2002, 22, 54-61). In clinical trials, the CGRP antagonist BIBN4096BS has been shown to be effective in treating acute attacks of migraine (Olesen et al., New Engl. J. Med., 2004, 350, 1104-1110) and was able to prevent headache induced by CGRP infusion in a control group (Petersen et al., Clin. Pharmacol. Ther., 2005, 77, 202-213).

CGRP-mediated activation of the trigeminovascular system may play a key role in migraine pathogenesis. Additionally, CGRP activates receptors on the smooth muscle of intracranial vessels, leading to increased vasodilation, which is thought to contribute to headache pain during migraine attacks (Lance, Headache Pathogenesis: Monoamines, Neuropeptides, Purines and Nitric Oxide, Lippincott-Raven Publishers, 1997, 3-9). The middle meningeal artery, the principle artery in the dura mater, is innervated by sensory fibers from the trigeminal ganglion which contain several neuropeptides, including CGRP. Trigeminal ganglion stimulation in the cat resulted in increased levels of CGRP, and in humans, activation of the trigeminal system caused facial flushing and increased levels of CGRP in the external jugular vein (Goadsby et al, Ann. Neurol., 1988, 23, 193-196). Electrical stimulation of the dura mater in rats increased the diameter of the middle meningeal artery, an effect that was blocked by prior administration of CGRP(8-37), a peptide CGRP antagonist (Williamson et al., Cephalalgia, 1997, 17, 525-531). Trigeminal ganglion stimulation increased facial blood flow in the rat, which was inhibited by CGRP(8-37) (Escott et al., Brain Res. 1995, 669, 93-99). Electrical stimulation of the trigeminal ganglion in marmoset produced an increase in facial blood flow that could be blocked by the non-peptide CGRP antagonist BIBN4096BS (Doods et al., Br. J.Pharmacol., 2000, 129, 420-423). Thus the vascular effects of CGRP may be attenuated, prevented or reversed by a CGRP antagonist.

CGRP-mediated vasodilation of rat middle meningeal artery was shown to sensitize neurons of the trigeminal nucleus caudalis (Williamson et al., The CGRP Family: Calcitonin Gene-Related Peptide (CGRP), Amylin, and Adrenomedullin, Landes Bioscience, 2000, 245-247). Similarly, distention of dural blood vessels during migraine headache may sensitize trigeminal neurons. Some of the associated symptoms of migraine, including extracranial pain and facial allodynia, may be the result of sensitized trigeminal neurons (Burstein et al., Ann. Neurol. 2000, 47, 614-624). A CGRP antagonist may be beneficial in attenuating, preventing or reversing the effects of neuronal sensitization.

To a suspension of 11 (465 g, 96% wt, 0.99 mol) in iPAc (4.6 L) was added 5% aqueous K3PO4 (4.6 L). The mixture was stirred for 5 min. The organic layer was separated and washed with 5%> aqueous K3PO4 (4.6 L) twice and concentrated in vacuo and dissolved in acetonitrile (1.8 L).

To another flask was added 14 (303 g, 91.4 wt%>), acetonitrile (1.8 L) and water (1.8 L) followed by 10 N NaOH (99 mL). The resulting solution was stirred for 5 min at room temperature and the chiral amine solution made above was charged to the mixture and the container was rinsed with acetonitrile (900 mL). HOBT hydrate (164 g) was charged followed by EDC hydrochloride (283 g). The mixture was agitated at room temperature for 2.5 h. To the mixture was added iPAc (4.6 L) and organic layer was separated, washed with 5%> aqueous NaHC03 (2.3 L) followed by a mixture of 15%> aqueous citric acid (3.2 L) and saturated aqueous NaCl (1.2 L). The resulting organic layer was finally washed with 5%> aqueous NaHC03 (2.3 L). The organic solution was concentrated below 50 °C and dissolved in methanol (2.3 L). The solution was slowly added to a mixture of water (6 L) and methanol (600 mL) with ~ 2 g of seed crystal. And the resulting suspension was stirred overnight at room temperature. Crystals were filtered, rinsed with water/methanol (4 L, 10 : 1), and dried under nitrogen flow at room temperature to provide 15 (576 g, 97 % yield) as trihydrate.

To a suspension of 13 (10 g, 98 wt%, 23.2 mmol) in MTBE (70 mL) was added 0.6 N HCI (42 mL). The organic layer was separated and extracted with another 0.6 N HCI (8 mL). The combined aqueous solution was washed with MTBE (10 mL x3). To the resulting aqueous solution was added acetonitrile (35 mL) and 14 (6.66 g, 99 wt%). To the resulting suspension was neutralized with 29 % NaOH solution to pH 6. HOPO (0.26 g) was added followed by EDC hydrochloride (5.34 g). The mixture was stirred at room temperature for 6-12 h until the conversion was complete (>99%). Ethanol (30 ml) was added and the mixture was heated to 35 °C. The resulting solution was added over 2 h to another three neck flask containing ethanol (10 mL), water (30 mL) and 15 seeds (0.4 g). Simultaneously, water (70 mL) was also added to the mixture. The suspension was then cooled to 5 °C over 30 min and filtered. The cake was washed with a mixture of ethanol/water (1 :3, 40 mL). The cake was dried in a vacuum oven at 40 °C to give 15 trihydrate (13.7 g, 95%) as crystals.

Abstract

The development of a scalable asymmetric route to a new calcitonin gene-related peptide (CGRP) receptor antagonist is described. The synthesis of the two key fragments was redefined, and the intermediates were accessed through novel chemistry. Chiral lactam 2 was prepared by an enzyme mediated dynamic kinetic transamination which simultaneously set two stereocenters. Enzyme evolution resulted in an optimized transaminase providing the desired configuration in >60:1 syn/anti. The final chiral center was set via a crystallization induced diastereomeric transformation. The asymmetric spirocyclization to form the second fragment, chiral spiro acid intermediate 3, was catalyzed by a novel doubly quaternized phase transfer catalyst and provided optically pure material on isolation. With the two fragments in hand, development of their final union by amide bond formation and subsequent direct isolation is described. The described chemistry has been used to deliver over 100 kg of our desired target, ubrogepant.

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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 30 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri, Dr T.V. Radhakrishnan and Dr B. K. Kulkarni, etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him Open superstar worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international,
etc in organic chemistry are some most read blogs He has hands on experience in initiation and developing novel routes for drug molecules
and implementation them on commercial scale over a 30 year tenure till date Dec 2017, Around 35 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 9 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 50 Lakh plus views on dozen plus blogs, He makes himself available to all, contact him on +91 9323115463, email amcrasto@gmail.com, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 19 lakh plus views on New Drug Approvals Blog in 216 countries......https://newdrugapprovals.wordpress.com/ , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc

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